1. Field of the Invention
The present invention relates to an interference preventing apparatus and, more specifically, to an apparatus for preventing a movable member and a structural member of an NC machine tool from interfering with each other in any of plural interfering relationships.
2. Description of Related Art
An interference preventing apparatus as shown in FIG. 8 is conventionally known as the interference preventing apparatus of the aforesaid type. As shown in FIG. 8, the interference preventing apparatus 50 is accommodated in a numerical controller 60 of an NC machine tool, and includes an interference area defining section 51, an interference area data storage section 52, an interference checking section 53 and an alarm section 54.
In the following description, it is assumed that an NC lathe is employed which includes a tool post for holding a tool, a headstock for rotatably supporting a spindle, and a tailstock disposed in opposed relation to the headstock for rotatably supporting a tailstock spindle, and the interference preventing apparatus 50 is adapted to prevent interference between the tool and a spindle portion (including the spindle and a chuck attached to the spindle) and interference between the tool and a tailstock portion (including the tailstock and the tailstock spindle) in the NC lathe.
The numerical controller 60 further includes an NC program storage section 61, a program analyzing section 62, a tool offset amount storage section 63 and a drive controlling section 64. The interference area defining section 51, the interference checking section 53, the alarm section 54 and the drive controlling section 64 are connected to an input/output device 71 including an operating panel and a CRT. The drive controlling section 64 is connected to driving means 72 including a servo motor and a spindle motor for moving the tool post.
The NC program storage section 61 stores therein preliminarily generated NC programs. The tool offset amount storage section 63 stores therein a tool offset amount for each tool held by the tool post.
The program analyzing section 62 sequentially analyzes the NC programs stored in the NC program storage section 61, extracts a command related to a movement position of the tool post, and outputs the extracted command to the drive controlling section 64.
The drive controlling section 64 controls the movement of the tool post and the rotation of the spindle. For the movement of the tool post, for example, the drive controlling section 64 generates target movement position data for the tool post on the basis of the command signal outputted from the program analyzing section 62 and the tool offset amount of the tool stored in the tool offset amount storage section 63, and then properly processes the target movement position data for generation of a control signal, which is in turn outputted to the driving means 72 for controlling the driving means 72.
Where a pulse handle provided on the operation panel of the input/output device 71 is operated for manual operation, for example, a pulse signal is outputted to the drive controlling section 64 from the pulse handle. Then, the drive controlling section 64 generates target movement position data on the basis of the number of pulses of the received pulse signal, and properly processes the target movement position data for generation of a control signal, which is in turn outputted to the driving means 72 for controlling the driving means 72.
The tool post target movement position data generated by the drive controlling section 64 is outputted to the interference checking section 53.
The interference area defining section 51 defines interference areas where the tool is likely to interfere with the spindle portion and the tailstock portion within a area where the tool held by the tool post is movable. For example, the interference areas are interactively defined by means of the input/output device 71, and data indicative of the interference areas is stored in the interference area data storage section 52. The interference areas are represented by position coordinate data which defines the contours of the spindle portion and the tailstock portion in a machine coordinate system, and areas within the contours are regarded as the interference areas.
The interference checking section 53 checks for a possibility of the interference between the tool and the spindle portion and a possibility of the interference between the tool and the tailstock portion upon reception of a process implementation signal from the program analyzing section 62 in an automatic operation or upon reception of a process implementation signal from the input/output device 71 in the manual operation.
More specifically, the interference area data is read out of the interference area data storage section 52, and a tool offset amount of a tool indexed in a machining position is read out of the tool offset amount storage section 63. Then, movement target positions of an edge of the tool in the machine coordinate system are sequentially calculated on the basis of the tool offset amount thus read out and the tool post target movement position data outputted from the drive controlling section 64. The movement target position data thus calculated is compared with the interference area data for determining whether or not the movement target positions are located within the interference areas. If any of the movement target positions is located within the interference areas, the possibility of the interference is confirmed.
Where the possibility of the interference between the tool and the spindle portion or the tailstock portion is confirmed, the interference checking section 53 outputs a drive stopping signal (interference confirming signal) to the drive controlling section 64, and outputs an alarm display signal (interference confirming signal) to the alarm section 54.
The alarm section 54 displays an alarm on the CRT of the input/output device 71 upon reception of the alarm display signal from the interference checking section 53.
In the interference preventing apparatus 50 having the aforesaid construction, the interference checking section 53 determines whether or not the tool has a possibility to interfere with the spindle portion and the tailstock portion in the automatic operation or in the manual operation. If the possibility of the interference is confirmed, the drive stopping signal is outputted to the drive controlling section 64 from the interference checking section 53 for stopping the movement of the tool post. Thus, the interference between the tool and the spindle portion and the interference between the tool and the tailstock portion are prevented. Further, the alarm display signal is outputted to the alarm section 54 from the interference checking section 53, and the alarm is displayed on the CRT.
However, the conventional interference preventing apparatus 50 described above is given an option to perform or not to perform the interference checking operation for all of the interference areas at a time. In other words, the interference preventing apparatus 50 is not given an option to perform or not to perform the interference checking operation for each of the interference areas and, therefore, suffers from the following drawbacks.
After exchange of the tool attached to the tool post, for example, the tool offset amount should be reset for a tool newly attached to the tool post. A tool offset amount setting operation is performed by employing a preseter or by actually machining a workpiece. In either case, the tool post should be moved toward the spindle for the setting of the tool offset amount.
If the interference checking section 53 is permitted to perform the interference checking operation when the tool offset amount setting operation is performed, the interference checking section 53 calculates the target movement positions of the edge of the tool on the basis of the tool offset amount set before the tool exchange. Therefore, the possibility of the interference is erroneously confirmed even if there is actually no possibility of the interference between the tool and the spindle portion. Thus, the tool offset amount setting operation cannot smoothly be performed.
On the other hand, if the interference checking section 53 is prohibited from performing the interference checking operation when the tool offset amount setting operation is performed, an operator moves the tool while paying careful attention to the interference between the tool and the spindle portion. However, the operator tends to be careless about the interference between the tool and the tailstock portion on the opposite side, so that the tool may collide against the tailstock portion. Therefore, the interference preventing apparatus 50 fails to serve for the intended purpose. Thus, the conventional interference preventing apparatus 50 suffers from poor operability.
In view of the foregoing, it is an object of the present invention to provide an interference preventing apparatus which features an improved operability.
In accordance with the present invention to achieve the aforesaid object, there is provided an interference preventing apparatus for use in an NC machine tool comprising at least one movable member, a numerical controller for controlling an operation of the movable member, and at least one structural member which is likely to interfere with the movable member, the at least one movable member and the at least one structural member having plural interfering relationships with respect to each other. The interference preventing apparatus is adapted to prevent interference between the movable member and the structural member, and comprises: an interference area defining section for defining an interference area where the movable member is likely to interfere with the structural member within a area where the movable member is movable; an interference area data storage section for storing therein data indicative of the interference area defined by the interference area defining section; and an interference checking section which performs an interference checking operation to check for a possibility of the interference between the movable member and the structural member in any of the plural interfering relationships on the basis of the interference area data stored in the interference area data storage section and data indicative of a target movement position of the movable member controlled by the numerical controller and, if the possibility of the interference is confirmed, outputs an interference confirming signal to the numerical controller; wherein the interference checking section receives a selection signal externally inputted to select at least one of the plural interfering relationships between the at least one movable member and the at least one structural member, and performs the interference checking operation only for the selected interfering relationship.
According to the present invention, the interference area defining section defines the interference area where the movable member is likely to interfere with the structural member within the area where the movable member is movable, and the data indicative of the defined interference area is stored in the interference area data storage section.
Then, the interference checking section checks for the possibility of the interference between the movable member and the structural member in any of the interfering relationships on the basis of the interference area data stored in the interference area data storage section and the data indicative of the target movement position of the movable member controlled by the numerical controller. If the possibility of the interference is confirmed, the interference confirming signal is outputted to the numerical controller. Upon reception of the interference confirming signal, the numerical controller stops the driving and controlling of the movable member.
When the interference checking section receives the selection signal externally inputted to select at least one of the plural interfering relationships between the at least one movable member and the at least one structural member, the interference checking section performs the interference checking operation only for the selected interfering relationship.
Where there are plural interfering relationships between the at least one movable member and the at least one structural member, an interfering relationship to be subjected to the interference checking operation can be selected by the external input in the interference preventing apparatus. Therefore, when the aforesaid tool offset amount setting operation is performed, for example, a particular interfering relationship not to be subjected to the interference checking operation (in the aforesaid case, the interfering relationship between the tool and the spindle portion) can be excluded, so that the interference checking operation is not performed for this particular interfering relationship. Thus, the tool offset amount setting operation can smoothly be performed, while the interference checking operation is kept performed for the other interfering relationships (in the aforesaid case, the interfering relationship between the tool and the tailstock portion). Accordingly, the collision of the tool against the tailstock portion due to an operation mistake can assuredly be prevented, so that the tool offset amount setting operation can safely be performed.
The plural interfering relationships between the at least one movable member and the at least one structural member herein include interfering relationships between one movable member and two or more structural members, interfering relationships between two or more movable members and one structural member, and interfering relationships between two or more movable members and two or more structural members. For each of the interfering relationships, there is an option to perform or not to perform the interference checking operation.
Alternatively, the interference checking section may be adapted to receive a specific operation signal from the numerical controller when the NC machine tool is in a manual operation and, upon reception of the operation signal, be prohibited from performing the interference checking operation for an interfering relationship associated with the received operation signal.
In this interference preventing apparatus, when the interference checking section receives the specific operation signal from the numerical controller in the manual operation of the NC machine tool, the interference checking section is automatically prohibited from performing the interference checking operation for the interfering relationship associated with the received operation signal.
Where the interfering relationship to be subjected to the interference checking operation is selected from the plural interfering relationships by the external input, an operator""s input mistake cannot perfectly be eliminated. Therefore, there is a possibility that the interference checking operation is not performed for the intended interfering relationship due to the input mistake.
In the interference preventing apparatus having the aforesaid construction, the interfering relationship not to be subjected to the interference checking operation is automatically determined on the basis of the operation signal for operating the NC machine tool. Therefore, an inconvenience resulting from a human mistake can be eliminated, so that the operation can safely be performed.
In the present invention, the specific operation signal includes a preseter mount signal which is inputted to the numerical controller when a preseter is mounted in the NC machine tool for manually performing the tool offset amount setting operation with the use of the preseter.